We have continued to refine a protein idenfication software routine called "ProFound", which makes use of information from mass spectrometric peptide maps to provide identificaton of proteins whose sequence is stored in one of the publicly accessible databases. This program, which was written by Wenzhu Zbang (a member of our Research Resource) is publicly available over the World Wide Web (http://chait-sgi.rockefeller.edu). The program is the only protein identification software currently available that uses robust probability criteria to rank the protein identification calls. In addition, it is the only software currently available that can identify mixtures of proteins using objective criteria. ProFound is being widely used by scientists all over the world. A paper describing the software is currently under preparation.